Distribute derivative of sum with constant term after substitution

[Carl Sandrock]

If I do

import sympy
k, V, Vprime = sympy.symbols('k, V, Vprime')

print sympy.diff(k + V(t), t)

I get Derivative(V(t), t) as I expect - the derivative distributes and the constant term has zero derivative.

However, if I construct an equivalent expression via substitution, simplify does not distribute the derivative. How can I get the same result via substitution as when I evaluate the expression directly?

sympy.diff(Vprime(t)).subs({Vprime(t): k + V(t)}).simplify()

returns Derivative(k + V(t), t).

(also posted on Stackoverflow) 

[Kalevi Suominen]

Perhaps you could use ``doit()``` instead of ``simplify()``.

 

[Carl Sandrock]

That worked perfectly, thank you very much!